The overall objective of research proposed here is elucidation of relations between enzyme structural transitions and enzyme catalysis. In particular, we will use elution gel chromatography to define assembly of the oligomeric regulatory enzymes arginine decarboxylase from Escherichia coli and deoxycytidylate deaminase from staphylococcus aureus under systematically varied solution conditons. This will permit us to assess affects of those alterations in conditions lupon enzyme strucutre,, as measured by changes in the energetics of assembly. The steady-state kinetic properties of these enzymes will be measured under conditions identical to those used for assemnly studies. Variations will include pH, temperature, salt concentration, addition of regulatory ligands, and variations in substrate structure. We will utilize both native and specifically chemically modified enzymes. Effects of these variations catalytic properties will be determined by use of the theory of linked functions to analyze the data and will be correlated with resultis of the assembly studies to define relations between structural transitions and catalysis. We will seek to define the location and types of forces important for catalysis and to delineazte roles for specific enzyme groups and regions. These results will provide important insights into mechanisms of catalysis and regulation of metabolic processes. Since enzyme catalysis of specific chemical reactions forms the basis for living systems, it is important that it be understood in the fullest physical-chemical terms.